1. Field of the Invention
The invention relates to a flat knitting machine having two opposed needle beds, and a carriage traversible along the beds, and more particularly to a system for transferring loops from the needles of one of the needle beds to the needles of the other needle bed.
2. Description of the Prior Art
A loop transferring cam system of the kind comprising a transfer cam having one nose and a receiving cam having two noses of different heights on the carriage has already been described, as for instance in German Pat. No. 660,568. This loop transferring cam system permits loop transfer to be effected only when the carriage traverses in one direction, whereas for expanding the loops that are to be transferred the needles from which the loops are transferred as well as the needles which are to receive loops must be lifted. Satisfactory loop transference and simultaneous knitting action during the same carriage traverse is impossible of attainment with this prior art system of cams.
Completely symmetrical loop transferring cam systems have also been proposed which permit loops to be transferred in a leading or trailing position to the stitch cam system during carriage traverse. These loop transferring cam systems comprise transfer cams having two noses of equal height, the leading nose in either direction of carriage traverse being used for expanding the loops that are to be transferred and the trailing nose being used for actually effecting the transfer. Loop transferring cam systems of this design have the drawback that loop expansion is not satisfactory when needles fitted with loop expanders are used.
Another problem which arises in loop transfer is that previously special devices were needed for opening the latches on the loop receiving needles. The flat knitting machine described in German Pat. No. 660,568 also requires a special device for opening the latches.
A known device for opening the latch on the receiving needle is a wire hook attached to the carriage and adapted with its point to slide along the underside of the comb of the tracked needle bed and to engage the needle directly below the needle hook. The external shape of the wire hook is such that it will retract the latch and retain it in open position during the following transferring action. In order to permit the wire hook to move into the required position the needle bed comb must be considerably undercut and in consequence weakened. If the wire loop has been slightly bent by some minor bump the latches will cease to open as required and they may even be damaged.
An alernative device for opening the latches on the receiving needles consists of flat or round brushes affixed to the carriage. However, even these brushes are not entirely reliable in opening the latches because they cannot retain the open latches during loop transference since the receiving needle is not lifted higher than into tuck position and the latch in this position is still inside the comb of the bed and behind the transferring needle which is in clearing position.
Another known method of opening the latches of the receiving needles uses magnets attached to the carriage, but this is a complex and expensive arrangement. Finally, it has been proposed for instance in the published specification of German Patent Application No. 1,585,391 to open the latches by means of the opposing needles. This has the drawback that during traverse of the carriage in one direction it is impossible to knit and to transfer loops at the same time.